Method of abrading workpieces



July 7, 1936. I R.,A. ST. JOHN METHOD OF ABRADINIG WORKPIEGES- Fiid July 19, 1952 Patented: July 7, 1936 UNITED STATES PATENT OFFICE signor The Heald Machine Company,

Worcester, Mass, a corporation of Massachusetts Application July 19, 1932, Serial No. 623,401

, tion is desired. One of these machines grinds the internal surface of the workpieceapproximately to the desired size and uses a grinding wheel suitable for rough or rapid grinding. The

workpiece is then removed from the first' machine and positioned in a second machine where ya polishing or finishing operation, by a wheel suitable for this apparatus, takes place in order to bring ,the workpiece exactly to size and to polish the surface of the workpiece. In addition to the labor required in handling the workpieces from one machine to the other, the time consumed in finishing each workpiece is materially increased by the necessity for successive operations in separate machines. Furthermore,

- when the workpiece is held in the usual form of chuck it is practically impossible to center the workpiece accurately in the chuck of the second machine for rotation about the same axis on which it was rotated in the first machine. Although the eccentricity of the workpiece in the second machine may be so small as to be generally negligible, nevertheless the finishing operation by the second machine, as a-result of the eccentricity, does not result in a smooth, even finishing operation over the entire area of the workpiece. It is accordingly the principal object of'the present invention to provide for a 9 grinding of the workpiece to approximately the desired size and for thereafter polishing the workpiece to obtain the desired finished surface,

while the workpiece is mounted in a single work supporting member. Although various machines have been developed in which the plurality ofgrinding wheels operate successively on the same surface of the workpiece, there is no successive grinding by independent grinding wheels of different character while the wheels or the cutting surfaces thereof are'in predetermined relation to the axis of rotation of the workpiece. 'In the greater number of machines which procure successive grinding operations on the workpiece, at least the last operation which provides for polishing the surface being ground, is performed by a wheel resiliently urged against the workpiece, therebymaking accurate sizing of the workpiece impossible. A further object of the invention is the successive grinding and polishing of a work- 5 piece surface in such a manner as to permit successive workpieces all to be reduced to the same predetermined size and at the same time to have a smooth surface. According to the present invention the work-- piece to be finished is mounted in and rotated by a work supporting member, and during its rotation in said member is successively rough ground or abraded substantially to the desired size. and thereafter polished by a further abrad- 15 ing operation, both of said abrading operations taking place without the necessity for the removal of the workpiece from the worksupporting member. The invention also involves the steps of rough grinding and thereafter finish grinding of the workpiece prior to the polishing operation, the grinding operations being procured successively to bring the workpiece substantially to the desired size. and the polishing operation thereafter providing the desired surface. In the abrading operationall the successive ,steps are procured while the workpiece is rotated about a single axis, as by supporting said workpiece in a single work supporting and rotating' member during the successive steps-of the abrading operation.

Other and further objects and advantages of the invention will appear from the followingdetailed description taken in connection with the accompanying drawing, in which:- 35

Fig. 1 is a diagrammatic view showing the relative position of the abrading wheels and the workpiece during the preliminary grinding operation. Fig. 2 is a view at right angles to the showing of Fig. 1 at the beginning of the abrading operation.

Fig. 3 is a view corresponding to Fig. 2, when the abrading operation is partially completed.

Fig. 4 is a view corresponding to Fig. 1, showing the position of the separate abrading wheels at a period in the grinding operation subsequent to that of Fig. 1. p

Fig. 5 is a view corresponding to Fig. 3 when a further step in the abrading operation has taken place, with the abrading wheels in the position of Fig. 4.

Like reference characters refer to like parts in the different figures.

Referring first to Fig. l, a workpiece a is mounted in a suitable work supporting and rotating member I, which, in the construction shown, is represented by a well known form of chuck. A pair of abrading wheels 2 and 3 are carried in spaced relation to each other on a grinding wheel spindle 4, the spacing being such that the abrading wheel 2 may be reciprocated over the surface of the workpiece a between the full and dotted line positions of Fig. 1, without bringing the abrading wheel 3 into engagement with the same surface of the workpiece.

In carrying out the method of the present invention the. abrading wheel 2 preferably has a suitable grain for rough or rapid grinding of the workpiece substantially to the desired size, and the abrading wheel 3 has a grain or formation which is suitable for polishing the surface of the workpiece without substantial removal of the material of the workpiece, in order to provide the v desired finished surface for the workpiece.

The first step in the novel method consists in rough grinding of the surface 5 of the workpiece to a size somewhat smaller than the finished size by the grinding wheel 2, which as above stated, is suitable for rapid grinding of the surface of the workpiece. Referring to Fig. 2, the full line 5 represents the internal surface at the workpiece at the beginning of the abrading operation prior to the rapid grinding, and' the dotted line 6 represents the amount of inaterial removed by the wheel 2 during the rough or rapid grinding operation. It will be apparent that, during this rough grinding, which takes place as rapidly as possible, for the. purpose of removing the material from the workpiece in the shortest possible time, the abrading wheel 2 is reciprocated back and forth over the surface of the workpiece a between the full and dotted line positions of Fig. 1, and is also moved radially against the surface of the workpiece to provide a cross-feed movement for maintaining contact between the surface of the workpiece a and the wheel. During the grinding by the wheel 2, the work supporting member I provides for rotation of the workpiece about the normal axis of said workpiece.

After the completion of the first step in the method, that is, the rough grinding of the workpiece, said workpiece is in the condition represented by Fig. 3. The line 6' of Fig. 3 represents the internal surface of the workpiece at the completion of the rough grinding operation, and accordingly is in the same position relative to the outside surface 1 of the workpiece as the dotted line 6 of Fig. 2. The dotted line 5' of Fig. 3 represents the inside surface of the workpiece before the abrading operation was begun,

corresponding to line 5 of Fig. 2, and the dotted 1 line 8 represents the desired inside surface of the workpiece at the completion of the second step in the abrading operation.

This second step involves grinding of the internal surface of the workpiece from the surface 6' of Fig. 3 to a. surface 8' represented by the dotted line 8, and during this grinding the material of the workpiece is removed at a materially slower rate than that of the rough grinding operation, in order that the surface of the workpiece may be substantially smoother and with less scratches thereon when said workpiece is reduced to the size represented 'by the dotted line 8. This slower or finish grinding operation may result either from a slower radial or cross feed movement of the grinding wheel against the surface of the workpiece. or from a slower reciprocation of the wheel 2 over the surface of the workpiece. This final or finish grinding of the workpiece will reduce said workpiece substantially to the desired size, and as indicated removes a relatively small amount of material from the workpiece.

After the workpiece is reduced to the diameter represented by the dotted line 8 of Fig. 3 the abrading wheels 2 and 3 are shifted axially relative to the workpiece a to bring the abrading wheel 3 into-engagement with the surface of the workpiece and to withdraw the abrading wheel 2 therefrom for the subsequent step in the abrading operation. This step, which consists in polishing the workpiece, is represented by Figs. 4 and 5 which show the abrading wheel3 in operative relation to the same surface of the workpiece upon which the grinding operations by wheel 2 were performed.

Referring particularly to Fig. 5, the dotted line 5' again represents the internal surface of the workpiece at the beginning of the abrading operation, the dotted line 6 represents the size of the workpiece at the end of the first step or rough grinding, and the'full line 8 represents the present size of the workpiece, that is, the size of the workpiece at the completion of the finish grinding operation. Since the polishing operation by the wheel 3 removes such a small amount .of material from the workpiece as to be negligible as compared to the amount of material removed during either of the grinding operations by the wheel 2, the line 8' also represents the finished size of the workpiece.

The above noted polishing step in the method of abrading workpieces consists in reciprocating the wheel 3 over the surface of the work, either with or without a radial or cross feed movement, said wheel 3 polishing the surface of the workpiece and thereby eliminating all scratches resulting from the grinding operation by the wheel 2, which as previously stated, is substantially coarser than the polishing wheel 3.

As will be apparent from a consideration of the drawing, the successive steps in the novel method above described all take place while the workpiece is 'supported in and rotated by the work supporting member I, and accordingly the said workpiece is rotated throughout the abrading operation on a single axis of rotation- The successive grinding operations, and thereafter the polishing opeeration thus occur while the workpiece is rotated about an axis concentric to. the surface being abraded. It will be noted that the mounting of the wheels 2 and 3 on a single wheel spindle also provide that the wheels 2 and 3 shall rotate about concentric axes. The grinding wheels 2 and 3 also are substantially the same diameter and since the axis of rotation of the wheels is in predetermined relation to the axis of rotation of the workpiece the cutting surface of the polishing wheel 3 will be in proper position for grinding as a result of axial shifting of the two wheels as a unit relative to the surface of the workpiece being ground.

The crossfeed movement above referred to, by which the grinding wheels are given a radial movement relative to the axis of rotation of the workpiece, is preferably procured by any suitable well known crossfeed mechanism, as' for example, that disclosed in the copending application of Taylor, Quimby and Lippard, Serial No. 623,400, filed July 19, 1932, now Patent No. 1,949,552, dated March 6, 1934, or in the patent to Taylor No. 1.682.673, dated August 28, 1928.

In either of these machines the crossfeed move- I ment of the grinding wheel is positively procured,

and "although there is a relative movement between the axis of rotation of the workpiece andthe axis of the grinding wheel, these axes, nevertheless, at all times in predetermined relation to each.other,-that is to say, the grinding wheel is positively urged against the surface of the workpiece rather than resiliently urged, as in the majority of machines which provide for a polishing operation.

From the foregoing it will be apparent that the novel methodresides in first abrading the workpiece rapidly as by a grinding operation to reduce theworkpiece. substantially to the desired size, and thereafter polishing the workpiece with ,asuitable polishing member to provide the desired finished surface on the workpiece, both the grinding and polishing being done without removal of the workpiece from the work supporting and rotating member, while the workpiece is rotated about a single axis. It will be further apparent that the grinding operation may include both a rough grinding and a finish grinding operation, thereby providing for rapid removal of the ;material of the workpiece until said workpiece approaches the desired size, and thereafter for slower removal of the material of the workpiece. As the workpiece reaches the desired size, the grinding operationis discontinued and the polishing wheel is set in operation for completing the workpiece.

I claim:--

1. In the art of abrading the internal surface of a workpiece, the improvement which consists in supporting the workpiece in a work-supporting member for rotation of said workpiece about a predeterminedaxis and in successively grinding and polishing the internal surface of said workpiece with separate abrading members rotatable about coincident axes while the workpiece is supported and rotated by said workholding member,

whereby---the axes'of rotation of the workpiece and of thegrinding wheels are in predetermined relation to each other during both abrading operations. Y

2. In the art of abrading the internal surface of a workpiece, the improvement which consists in procuring a grinding operation on the internal surface of the workpieceby an abradingwheel suitable for grinding of the material of the workpiece and thereafter procuring a polishing operation on'the same surface of the workpiece by an abrading wheel suitable for polishing, both of saidabrading wheels beingrotated about coincident axes and both the grinding and polishing operations being performed while the workpiece is supported ,in a single work-supporting member and rotated by said member about a predetermined axis, the axes" ofrotation of'the workpiece and of the grinding wheels being in predetermined relation to each other during both abrading operati ns.

3. In the art 0 abradingthe internal surface of a workpiece, the improvement which consists in mounting the workpiece in a work-supporting member for rotation of said workpiece about the predetermined axis, reciprocating a rotating grinding wheel over an internal surface of the workpiece to procure a grinding operation thereon, and thereafter reciprocating a polishing wheel over the same surface of the workpiece to procure a polishing operation thereon, said wheels ,being rotated about coincident axes with. said axes in predetermined relation to the axis of rotation of the workpiece during both abrading operations, "both of said operations being performed while the workpiece is supported in and rotated by said work-supporting member. f

4. In the art of abrading the internal surface of a workpiece, the improvement which consists in mounting the workpiece in a work-supporting member for rotation of said workpiece about a predetermined axis, and in procuring successively a rough grinding and a finished grinding operation on the internal surface of said workpiece,

and thereafter by a separate abrading wheel procuring a polishing operation on the same surface of the workpiece, all of the operations being.

performed while the workpiece is supported in and rotated' by the work-support with the axis of rotation of the workpiece in predetermined relation to the axes of rotation of the abrading wheels, the latter being all rotated about coincident axes..

5. In the art of abrading the internal surface of a workpiece, the improvement which consists in mounting the workpiece in a work-supporting member for rotation of said workpiece about a predetermined axis and in procuring a rough 25 grinding operation on the internal surface of said workpiece with an abrading wheel, subsequently in procuring a finish grinding operation on the same surface of the workpiece with an abrading wheel and thereafter in polishing the same sur- 30 face of the workpiece with another abrading wheel, said wheels being rotated about coincident axes, all of said abrading operations being performed while the workpiece is supported in and rotated by the work-supporting member, with 35' grinding operation onthe same surface of the i workpiece with one abrading wheel and thereafter in'procuring a polishing operation on the' same surface of the, workpiece with a second abrading wheel, both of said wheels being rotated about coincident axes, all of said operations being performed while the workpiece is supported in and rotated by the work-supporting member with the axis of rotation of the workpiece in predetermined relation to the axes of rotation of the abrading wheels duringthe sev-- eral abrading operations. v

7. In the art of abrading the internal surface of a workpiece, the improvementwhich consists in mounting the workpiece in a work-supporting member for rotation of the workpiece about a predetermined axis and in reciprocating a rotating grinding wheel over the internalsurface of the workpiece to procure a grinding operationthereon, thereafter reciprocating a rotating grinding wheel over the same surface of the workpiece to procure a second grinding operation thereon at a different rate and subsequently reciprocating arotating polishing wheel over the same surface of the workpiece to procure a polis'hing operation thereon; saidwheels being rotated about coincident axes, all of said operations being performed while the workpiece is supported in and rotated by the work-supporting member with the axis of rotation of the workpiece in predetermined relation to the axes of rotation of the wheels.

8. In the art of abrading the internal surface of a workpiece, the improvement which consists in mounting the workpiece in a work-supporting structure for rotation of the workpiece about a predetermined axis and in procuring successive abrading operations on the same internal surface of the workpiece by reciprocating abrading members rotatable about coincident axes separately and successively over the surface of the workpiece while said workpiece is positioned in and rotated by the work-supporting structure, with the axes of rotation of the abrading members in predetermined relation to the axis of rotation of the workpiece.

9. In the art of abrading the internal surface of a workpiece, the improvement which consists in mounting the workpiece in a single work-supporting structure for rotation of the workpiece about a predetermined axis and procuring successive grinding operations on the internal surface of the workpiece by the reciprocation of a plurality of abrading wheels, rotatable about coincident axes,

separately and successively over the surface of the workpiece while the workpiece is positioned in and rotated by the work-supporting structure, with the axis of rotation of the workpiece in predetermined relationto the axes of rotation of the grinding wheels.

10. In the art of abrading the internal surface of a workpiece, the improvement which consists in mounting the workpiece in a work-supporting structure for rotation of the workpiece about a predetermined axis, reciprocating a rotating abrading wheel over the internal surface of the workpiece to procure a cutting operation, and thereafter reciprocating a second abrading wheel, rotatable about a coincident axis, over the same surface of the workpiece, to procure a second cut ting operation, both of said operations being performed while the workpiece is supported in and rotated by said work-supporting structure, with the axis of rotation of the work-piece in predetermined relation to the axis of rotation of the abrading wheels.

11. In the art of abradingthc internal surfaces of workpieces, the improvement which consists in mounting a workpiece in a work supporting structure for rotation of said workpiece about a predetermined axis, reciprocating a rotating abrading wheel 'over an internal surface of the workpiece to procure a cutting operation, and thereafter reciprocating a second abrading wheel rotatable on an axis coincident with that of the first abrading wheel over the same surface of the workpiece to procure a second cutting operation, both of said operations being performed while the workpiece is supported in and rotated by said work supporting structure with the axis 'of rotation of the workpiece and the axes of rotation of the abrading wheels in predetermined relation to each other.

RAYMOND A. ST. JOHN. 

